The story revolves around a group of students who are connected through a system called "Kizuna," which allows them to share and feel each other's pain. The system was created by a girl named Noriko, who was part of an experiment 12 years ago that connected the pain of 19 children. However, the experiment went wrong, and Noriko was the only one who received the damage from the other 18 children, forcing her to live with a system that numbs her pain and emotions.
The story follows Agata, a student who doesn't feel pain, as he becomes part of the Kizuna system and forms bonds with his classmates. Through various challenges and experiences, the students learn to empathize and understand each other's pain, eventually developing strong relationships.
As the story unfolds, the students discover the truth about the Kizuna system and Noriko's past. Noriko wants to connect the entire city to the system, believing it's the only way to achieve happiness through bonds with others. However, the students argue that it's not necessary and eventually help Noriko come to her senses.
In the end, the students are disconnected from the Kizuna system, and Noriko begins to feel emotions and pain again. The story concludes with the students forming new relationships and bonds, and Agata and Sidor developing feelings for each other.
Here are the key facts extracted from the text:
1. A girl kidnaps six students to test a system that shares pain between them.
2. The system is designed to achieve world peace by making people feel each other's pain.
3. The protagonist, Agata, is one of the kidnapped students and is immune to pain.
4. The other students are forced to share their secrets or face electric shocks, which are felt by all through the system.
5. Agata's secret is that he is afraid of dogs.
6. The bully, a popular and intelligent boy, is revealed to be a former victim of bullying.
7. A rich and intelligent girl, who is seemingly perfect, is revealed to be hiding her true self.
8. The students are forced to work together to find a missing boy, who is later revealed to be a masochist.
9. The students go on a camping trip, where they experience emotional pain and begin to change their behavior.
10. The protagonist's childhood friend, Noriko, is revealed to be connected to him through the system.
11. The students discover that the system is not just physical pain, but also emotional pain.
12. The teacher reveals that the system was originally tested on 19 children, but only one girl, Noriko, received the damage from the other 18 children.
13. The girl, Noriko, has to inject herself with a liquid to numb her pain and live normally.
14. The students infiltrate the facility and learn the truth about the system.
15. The protagonist says goodbye to his friends and thanks to the system, he was able to understand and remember his old friends.
16. The teacher reveals that the true result of the experiment was that the students can feel each other's pain even when not connected.
17. Noriko thinks that happiness is in the bonds with other people, but believes that the only way to achieve it is through the system.
18. Noriko wants to connect the entire city to the system, but the protagonist argues against it.
19. Noriko releases the pain of the protagonist and begins to feel everything again.
20. The anime ends with the protagonist and his friends starting to develop relationships, but the ending is left somewhat open.